A technique has been developed to measure constituent layers in a complex material mixture by centrifuging a sample of the material mixture in a capillary or other tube which contains a float. The float is preferably cylindrical and of a specific gravity which causes it to settle into the centrifuged mixture to a degree which creates a free volume annulus in the tube into which the layer, or layers to be measured will settle. The layers to be measured are thus physically elongated, and can be more easily and accurately measured. This technique is described in U.S. Pat. Nos. 4,027,660, issued June 7, 1977; 4,082,085 issued Apr. 4, 1978; 4,156,570 issued May 29, 1979; and others.
This technique, as described in the prior art, depends on the manufacturer's ability to hold the capillary tube ID's and the float OD's to very tight tolerances. The magnification factor for the elongated constituent layers, when the technique is used as preferred in its commercial form, is about 10.5. This means that any layer which is expanded by the technique will be 10.5 times longer using the float than it would be without using the float. In order to achieve this magnitude of elongation, the tube ID will be maintained at 0.06605 inch, and the float OD will be maintained at 0.06285 inch. Thus the annulus is preferably only sixteen ten thousandths of an inch thick. It will be appreciated that minor variations in either the tube ID or the float OD, especially if additive, can result in changes in the annulus thickness which can cause inaccurate readings. For example, a tube ID which is slightly oversize, i.e. 0.00016 inch too large, plus a slightly undersized float, i.e. 0.00011 too small, will result in a reduction of the observed band lengths in the annulus of 8%.